Fatboy404. You have picked a great calibre in 6.5x57. I faced this problem a short time ago as I was looking to get a rifle made. For simplicity I chose the 6.5x55 built on a 98 action with a 26" medium MAB barrel and a boyd laminated thumb hole stock. The 6.5x55 is about 63 thou shorter than the 6.5x57 and has a sharper shoulder and a longer neck. Cases are readily avaliable. With ADI 2209 I can safely get 129 grn hornady SST at 2950fps and the 140 grn Sierra BT at 2850fps. Fallow deer, goats and foxes have all fallen to the SST without any problems and it is flat shooting. Accuracy is superb. IMHO I think the 6.5 calibre is ideal for the majority of Australian game. Good luck with your project.

Wayne